1. Field of Invention
The present invention relates to a method for manufacturing a capacitor of a semiconductor device, and more particularly, to a method for manufacturing a capacitor of a semiconductor device, which is suitable for large scale integration of a semiconductor device by controlling the deterioration phenomenon of a diffusion barrier film caused by the thermal process which is a defect in the conventional art, and thus, improving the electrical characteristic of the capacitor.
2. Description of the Related Art
As a semiconductor device is integrated in large scale and the size of a cell is reduced, it becomes difficult to guarantee sufficient electrostatic capacity, which is proportional to the surface area of storage electrode.
In particular, in the DRAM device in which unit cell is composed of a MOS transistor and a capacitor, it becomes an important factor for integrating DRAM device in large scale to increase the electrostatic capacity of the capacitor which occupies most of the area on a chip and decrease the area simultaneously.
Therefore, in order to increase the electrostatic capacity of the capacitor, which is expressed as (Eo*Er*A)/T (here, Eo is permittivity of vacuum, Er is permittivity of dielectric film, A is an area of capacitor and T is a thickness of dielectric film), the surface area of a storage electrode, which is a lower electrode in a capacitor, is increased. However, it makes large scale integration difficult since the manufacturing process becomes complicated and the step coverage is increased.
Therefore, the dielectric film is formed out of ferroelectric such as Tantalum oxide film of high permittivity having high dielectric constant Er (Ta2O5), BST (Ba, Sr) film, PZT (PbZrTiO3) film, SBT (SrBi2Ta2O9) film or PLZT (PbLaZrTiO3) film, and the upper and lower electrodes are formed out of Platinum (Pt) or conductive oxide film.
Here, an anneal process of about 800.degree. C. with which the dielectric film formation process accompanies needs a diffusion barrier film which protects the reaction between an electrode material and a polysilicon plug being a contact plug.
However, a diffusion barrier film used recently is formed as TiN/Ti stack structure, and it reacts with the silicon during the thermal process at a high temperature and then forms a titanium silicide. And the diffusion barrier film can be destroyed due to the high tension stress occurring at that moment.
Therefore, the reaction occurs between the electrode material and the silicon where it makes a silicide with high resistance and deteriorates the electric characteristic of a capacitor.
Also, in a case that a platinum is used as an electrode material, since an oxide is formed as an oxygen of an oxide high dielectric diffuses through the platinum lower electrode and then reacts with Ti of lower limb TiN layer, the phenomena occur that the platinum film swells up and it peels off at the interface with TiN.
According to the conventional art, the method for manufacturing a capacitor of a semiconductor device has problems that the characteristic and the reliability of a semiconductor device are reduced since the characteristic of device is deteriorated due to the unnecessary reaction between a contact plug and an electrode. Furthermore, the productivity of a semiconductor device is reduced, and therefore, it becomes difficult to integrate the semiconductor device in a large scale.